1. Field of the Invention
The present invention relates generally to construction systems and, more particularly, to construction systems which employ a plurality of connectable precast modular units which are transported to a building site and erected to construct a building structure, such as a basement, a garage or a floor level suitable as part of a dwelling, or to construct a fire cistern (snow-melting tank), a stilted foundation and the like. The present invention also relates to a method and apparatus for forming precast modular units, and to a precast modular structure and method for constructing the precast modular structure.
2. Background Information
Heretofore, when a basement is being prepared for construction of houses, for example, the ground at a construction site of the basement is excavated, underground water is treated, concrete is poured to form a floor, reinforcing rods are carried to the site and assembled together with temporary frames for forming retaining walls, and concrete is then poured to form the retaining walls. Thereafter, while curing of the concrete is carried out to ensure strengthening of the concrete, a temperature control operation is conducted until the concrete is hardened.
The foregoing conventional method of preparing a basement has the following problems. After the concrete is cured, the temporary frames are disassembled and removed from the site, the concrete surface is repaired, and then the exterior of the concrete structure is entirely waterproofed. Such operations are complicated and take about 3 to 4 weeks to complete. Furthermore, concrete beams, a floor for reinforcement, etc. are required to be constructed at the upper portion of the basement in order to withstand the soil pressure from the exterior. As a result, there arises various problems, for example, poor operational efficiency, prolonged construction and increased cost.
Moreover, masonry and concrete constructions are difficult on building sites in some weather conditions. During cold weather, on-site masonry and concrete construction are generally impossible. On-site masonry and concrete construction can also be delayed by water and snow. These delays increase construction costs.
Methods of constructing basement or garage structures by integrally forming walls, ceilings and floors into a box-like shape and then transporting them to an installation site are known. However, such methods are difficult to carry out because of the difficulty in transporting the basement or garage structure to the installation site due to the large weight of the structure. Accordingly, it has been necessary to reduce the size of such prefabricated structures in order to reduce their overall weight for transportation purposes. As a result, such prefabricated structures enclose relatively small interior spaces and therefore fail to provide sufficient space for storage or living.